Aerojet Rocketdyne’s (AR) bid to pay $2 billion for United Launch Alliance (ULA) appears to have been declined by one of the two entities who have the ability to approve it. ULA, a Boeing-Lockheed Martin joint venture, which currently fields the Atlas V and Delta IV family of boosters, is working to launch the Vulcan Next Generation Launch System by 2019. Boeing appears to have declined Aerojet Rocketdyne’s offer – at a time when ULA is strengthening ties with the AR’s competition.

ULA has opened the door to NewSpace firm Blue Origin, and the company’s BE-3 and BE-4 rocket engines for potential use on Vulcan. Aerojet Rocketdyne’s AR-1 rocket engine is currently competing with the BE-4 for use on Vulcan’s first stage.

However, shortly after AR’s offer to purchase United Launch Alliance, ULA and Blue Origin announced that they would work to produce the BE-4. Representatives with ULA have told SpaceFlight Insider that the final decision as to which engine will power Vulcan aloft – would be made in 2016.

SpaceFlight Now’s Stephen Clark has reported that ULA, at present, appears to be leaning toward the BE-4. The cited reason is that, in terms of the rocket engine’s development, the AR-1 is two years behind the BE-4. With rival launch service provider SpaceX acquiring many new customers for their Falcon 9 rocket, time may be one of the more critical variables that ULA is considering in terms of the engine-selection process for Vulcan.

At present, AR supplies ULA with the RS-68A and RL-10 for the Delta IV second and Atlas V upper stage as well as the AJ-60A solid rocket boosters that are currently used on certain versions of the Atlas V.

However, with the ascent of Vulcan, the liquid-fueled RS-68A (used on the first stage of the Delta IV), RL-10B2 (Delta Cryogenic Second Stage) and RL-10C (Atlas V upper stage) are likely to no longer have a customer. A representative with Aerojet Rocketdyne has stated that – depending on the certification of Vulcan and when the last flight of the Delta IV takes place – these engines could still be in service until 2023 and perhaps longer.

As it currently stands, Vulcan will, initially, use a Centaur Upper Stage before progressing on to the Advanced Cryogenic Evolved Stage (ACES). The BE-3 is being considered for use on ACES.

ULA announced on Tuesday, Sept. 22 that the company has decided to go with Orbital ATK’s GEM 63/63XL solid rocket motors (as opposed to the aforementioned AJ-60A) for both the Atlas V and Vulcan launch vehicles. Meaning that the core contractors on Vulcan appear at present to be: ULA, Blue Origin and Orbital ATK.

Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology, Space.com, The Mars Society and Universe Today.